Field of Invention
The present invention relates to a twin spot welding apparatus. More particularly, the present invention relates to a twin spot welding apparatus for changing a welding pitch and a welding slope to perform welding so that it is possible to cope with a curved and sloped shape and to rapidly perform welding in a limited space and with minimum time.
Description of Related Art
In general, during a manufacturing process of a vehicle, various structure parts such as vehicle body panels molded by press are welded to complete an integrated vehicle body, painting and rust resistance works are performed on surfaces of the parts of the completed vehicle body in a painting process, and power train system parts and suspension, steering, and brake system parts are assembled and doors, a trunk lid, and a hood are assembled in an assembly process.
In addition, when vehicle body parts such as a roof, pillars, side panels, and opening unit flanges of vehicle body doors are welded in a vehicle body assembly process, spot resistance welding is widely used for welding two vehicle body panels.
In the spot resistance welding, pressure is applied to surfaces of vehicle body panels so that the vehicle body panels are deposited by electric resistance. In general, the spot resistance welding is performed by a C-type spot welding gun installed at a leading end of an arm of a spot welding robot.
In the above-described spot welding gun, a lower electrode and an upper electrode are formed on a body of the C-type spot welding gun. The upper electrode is installed on an upper side of the gun body to be connected to a driving cylinder for proving pressure.
The spot welding gun is positioned in a welding position in accordance with a behavior of the robot in a state where the gun body is installed at the leading end of the arm of the robot through an installing frame to perform spot welding on a welded object by an operation of the driving cylinder.
Particularly, in the spot resistance welding, due to development of a new vehicle, in order to automatically and repeatedly perform welding on a new welding point by the robot to which the spot welding gun is attached, a robot operator initially moves the robot to a position of an actual material once to determine a welding position and a welding angle of the spot welding gun, to set the welding position and the welding angle in the robot, and to program the welding position and the welding angle.
On the other hand, in a spot welding process for vehicle body assembly, since welding must be continuously performed on several tens to hundreds of welding points, it takes long and a work process is very complicated so that various methods of improving productivity, efficiency, and welding quality while reducing welding time are sought for.
However, in a conventional welding system, since it is possible to attach one welding apparatus to one robot in a robot arm so that welding may be performed only once every moment when the robot arm is moved, it takes long to perform welding on a predetermined number of welding points so that productivity and efficiency are deteriorated.
In order to prevent the productivity and efficiency from being deteriorated, a plurality of robots may be installed so that the robots may simultaneously move along the welding points to perform welding. However, when the plurality of robots that are expensive, that have complicated structures, and that require complicated control processes are used, installation and maintenance costs are increased, an excessive amount of energy is used, and a space occupation ratio of the robots is increased in a mass production line.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.